The prior art abounds with apparatuses for the measurement of irregular obejcts, for example of the type indicated above. These apparatuses have been based on a direct mechanical sensing of the forms and configurations of the object and have often been constructed in such a manner that the object may be locked in a fixed position by means of suitable anchorage devices and that a movable measurement arm provided, for example, with a V block at its free end, is then moved along the tube, the movements of the measurement arm being registered and used as a description of the configuration of the tube.
Machines of the type in which direct mechanical sensing of the object takes place cannot combine rapid measurement with high precision, and particularly not if it is required that the machine be of simple construction at the same time.